I believe 1955 has the advantage of not having many stars making it relatively affordable

well the '55 doesn't have Mantle, but it does have plenty of stars in it and also has the Sandy Koufax RC and the Roberto Clemente RC which are both pretty high dollar cards. the '56 has the Mantle which is pretty high dollar but other than that I don't think it has anything too crazy. It is a much larger set though. '56 I think is around 350 cards where the '55 is around 206.

Thanks everyone. I've narrowed it down to 3, the 48,55, and 56 sets. What would be a rough estimate for the amount of money I would need to spend on them individually?

The amount of $$$ you will have to spend depends on the condition of the cards you buy, and therefore will vary widely.

Personally, my advice for sets this old and expensive (and the strategy I follow) is to focus on centering rather than corners (since bad centering detracts from the visual appeal more), and to focus on cards in the EX to NM range (i.e. PSA 5 to PSA 7). Buy graded cards if you find ones you like and crack them out, but don't pay a premium for the label.

I really like the 1956 Topps design and the format that they used. In my opinion, besided the 1952 set, I think the 1956 is one of the most desirable set of the 50s. I sold my set on eBay a few years back and of course regret it. Just started picking up some commons so I can start working on the set again. Shoot me a PM and maybe we can do some trading in the near future.

I would go with '56 Topps, slightly over '55. The '56 Mantle is a great card from his signature season. If you want a good mix of RCs and a nice Mantle (with his '56 stat line on the back), I'd look at the '57 set as well.

I picked the 48 Bowman because it is something I am considering pursuing. It's a small set with some really nice cards in it and they can all be had in the raw form for a reasonable "won't break the bank" price. Musial and Berra are probably the most expensive and Musial can be had for around 300 for a nice one.